Heat cleaning of fibrous glass fabrics



May 31, 1966 H. s. FALLS HEAT CLEANING 0F FIBROUS GLASS FABRICS Original Filed May 23. 1960 2 Sheets-Sheet 1 R M w m A y QQ s whiowm tot 03% uqUEme May 31, 1966 H. s. FALLS 3,253,897

HEAT CLEANING OF FIBROUS GLASS FABRICS Original Filed May 23, 1960 2 Sheets-Sheet 2 Tia. E

Tia. E.

INVENTOR Helwy 5 5441.5

BY @M United States Patent Claims. (Cl. 65111) This application is a division of the application, Serial No. 31,051, filed May 23, 1960, now abandoned.

The present invention relates generally to the treatment of fabrics formed of inorganic fibers and more particularly to a hot-air impingement method and apparatus for removing organic substances from fiber glass fabrics in .the continuous finishing thereof.

Increasing use is being made of fibrous glass yarns in the manufacture of textile fabrics intended for draperies, curtains and insulation, as well as a fibrous base in coated fabrics and in reinforced plastics. Such fabrics have decided advantages over conventional, natural and synthetic materials, for they need no ironing, cannot shrink and do not burn. Moreover, fiber glass fabrics are readily washed, are stain resistant and dry well.

One cannot take full advantage of the excellent physical and chemical properties of glass fibers unless the fibers are protected to prevent breakage in mutual abrasion. Glass fibers, upon attenuation, form naturally into fine filaments having very smooth and slippery surfaces. The low surface coefficient of friction permits the glass fibers easily to move relative to each other. It is, therefore, the common practice protectively to coat the glass fibers with certain organic substances.

A typical organic coating, often referred to as the starch oil size or binder, serves to protect the glass fiber during throwing, beaming, quilling, twisting or weaving. The starch used may be of any of the starches familiar to the textile technologist and may include slightly hydrolyzed or dextrinized starches. The oil in the starch binder is generally a lubricating oil of vegetable origin, such as castor, hydrogenated cottonseed, olive or coconut. In addition to these primary components, the binder may contain in extremely small amounts, one or more substances such as gelatine, bor-ax, polyvinyl alcohol, cationic surface active materials and dispersing agents.

The size is applied to the glass fiber by the yarn producer as the fiber is being formed. After the yarn has been woven into a greige fabric and is ready for the application of permanent colors and other finishing operations, it becomes essential first to remove all of the organic material from the glass. This is necessary in order to develop maximum adhesion between the glass fiber surfaces and the finishes. These organic solids which must be removed range from 0.5 percent to 4.0 percent on commercial glass yarns with the starch oil base. Any additional organic materials, such as warp sizings or oils put on by the weaver must also be completely removed.

For the purpose of removing the size, it has hitherto been the practice to burn off the organic solids, this being accomplished by passing the fabric through an oven operating at intenseheat. Air or oxygen is bled into the oven at such a rate that the organic material is ignited and burned fromvthe glass. -Igniti0n occurs within a fairly narrow zone.

This size removal technique, known commercially as Coronizing has a number of serious drawbacks which not only serve to slow down the finishing process but also to degrade the resultant fabric. When the organic solids are burned off, it has been found that residual carbon deposits are formed on the surface of the glass. These carbon deposits result from the incomplete combustion 3,253,897 Patented May 31, 1966 of 'the starches and hydrogenated cottonseed oil and other organic materials used in the binder and sizes. Not only does this tend to discolor or yellow the fabric, but the discoloration is non-uniform.

While attempts have been made to bring about more complete combustiomthis usually involves higher ignition temperatures. The increase in temperature, however, acts to Weaken and degrade the physical properties of the fiber glass. Another disadvantage of the Coronizing method is that it is relatively slow, ranging from to 65 feet per minute depending on the weight of the fabric and the type of yarn incorporated therein. Since accordingly.

I resulting from prior techniques.

the Coronozing oven constitutes the first stage in a sequence of finishing operations, no matter what the speed capabilities of the finishing equipment, the slow speed imposed by the burning-off operation limits the speed through the succeeding stages.

Another variable introduced by the burning-off operation arises from the fact that as there is considerable variation in the amount of binder in the glass fabric entering the oven, the temperature of ignition will vary It becomes difficult, therefore, to control and maintain a uniform fabric surface temperature.

In view of the foregoing, it is the primary purpose of the present invention to provide a new and improved technique and apparatus for heat-cleaning fibrous glass fabrics which obviate the disadvantages of prior methods.

More specifically, it is an object of the invention to provide a hot-air impingement technique for effectively cleaning glass fabrics uniformly and at a relatively high speed, without the deposition of carbon.

A further object of the invention is to provide a machine for the hot-air impingement cleaning of fiber glass fabrics wherein more accurate and uniform temperature control is made possible and wherein a greater and better air supply makes for more rapid oxidation of carbon.

A significant feature of the present invention resides in the fact that the organic sizes may be removed more rapidly and that the resultant fabric is not only cleaner but it is also of a tensile strength superior to the fabrics In actual practice fabrics may be cleaned at a rate of feet per minute and over, as compared to conventional rates of 25 to 65 feet per minute.

Briefly stated, these objects are attained in a cleaning system in which the greige fiber glass fabric web is first scoured and dried for a pre-reduction in organic content. The scoured web then passes at high speed through a hot-air impingement chamber wherein hot-air at a high temperature is delivered to both sides of the fabric by a series of delivery and exhaust nozzles. The fabric passes continuously in open width through the length ofthe chamber, the air being recirculated by fans and reheated for succeeding delivery by a heating unit outside the chamber.

Ignition within the chamber does not occur, the organic materials being removed from the surface of the glass by a scrubbing action of the impinging air and by volatilization. Removal of the organic substances is effected not within a narrow zone but uniformly throughout the entire area of the fabric web within the chamber.

For a better understanding of the invention as well as other objects and further features thereof, reference is made to the following detailed description to be read in conjunction with the accompanying drawing, wherein:

FIG. 1 is a flow diagram illustrative of the basic elements of a glass fiber fabric cleaning system in accordance with the invention.

FIG. 2 is a longitudinal sectional view of a hot-air impingement chamber in accordance with the invention.

FIG. 3 is an end view of the chamber.

Referring now to FIG. 1, the greige fabric 10, which is coated with organic material is drawn from an unwinder roll 11 and is first conveyed through a scouring unit 12 for prereduction in organic content. The scouring unit may be a standard open width Washer such as a Tensitrol machine manufactured by the Rodney Hunt Machine Co. of Orange, Mass, adapted for maximum washing efiiciency at high speeds. Washing may. be effected by water or with suitable detergents depending on the organic material, to remove 60 to 90 percent of the original size and binder.

The Wet pre-scoured fabric taken from the washing unit then passes through squeeze rolls 13 into a suitable high-temperature drying unit 14. Thereafter, the dried fabric is fed into a hot air impingement chamber 15. The moving fabric Web 10 is maintained in open width condition in chamber 15 and is subjected to tension therein by a suitable tension unit 16, one being placed at the entrance to the chamber 15, as shown, and the other at the exit end (not shown).

Chamber 15, as best seen in FIGS. 2 and 3, comprises an upper bank 17 of nozzles 17 to 17 and a lower and parallel bank 18 of nozzles 18 to 18 The fabric web enters the chamber through a rectangular inlet port 19 and exits through a rectangular outlet port 20, the.

web being centered relative to the two banks of nozzles.

The nozzles are arrayed at equi-spaced positions in the direction of web movement and are so interconnected by conduits or manifolds (not shown) that the odd numbered nozzles (i.e., 17 17 17 etc.) on the upper bank constitute suction or exhaust nozzles to draw gases and particles from the web, while the even numbered nozzles (i.e., 17 17 17 etcl) constitute delivery or pressure nozzles to project heated air onto the surface of the moving web, the air impinging on the surface causing the organic material thereon to volatilize.

The distribution of nozzles on the lower bank 18 is the reverse of that on the upper. That is, the odd numbered nozzles (18 18 etc.) are pressure nozzles and the even numbered nozzles (18 18 etc.) are suction nozzles.

Thus, as the fabric is conveyed through the chamber, each transverse zone on the fabric is subjected to a succession of impingement and suction actions along the array of nozzles. As 'a consequence of this repetitive activity, by the time a given fabric zone reaches the exit port, it has been thoroughly cleaned despite the high speed of operation, whereas in conventional burning or Coronizing ovens all cleaning takes place at a single position within the oven.

The delivery nozzles are supplied under pressure with heated air by a pump 21 acting in conjunction with a heater 22. Heater 22 may be in the form of gas burners, although any suitable heat source, such as an electrical furnace capable of heating large volumes of air to the necessary temperature (up to 1400 F.) may be used. The heated air mixed with the volatilization products from the organic substances as well as particles therefrom is exhausted from the chamber. T-o effect heating economy, the heated gases taken from the chamber are partially recirculated by means of a suction fan 23. The recirculated gases are purified by means of a particle remover or filter 24 and are reheated to the proper tem perature before being re-delivered into the chamber.

In some instances it may be desirable to provide a post-scouring operation by means of a second openwidth washing unit 25 for the purpose of removing water soluble salts created or leached out from the glassduring heat treatment. Such residual salts may interfere with good lamination of fiber glass industrial fabrics.

The hot-air impingement action serves not only to clean the fabric but may also be used to soften and relax the fiber glass, thereby permanently setting the glass yarns in the configuration of the weave. This crimping effect results in a wrinkle-proof fabric. Relaxation of the fabric depends on the internal fiber temperature, the

time of exposure to such temperature, the type of glass and several other factors. In some cases it may be desirable to clean and yet avoid relaxation of the glass fibers.

A cleaning and weave setting operation will be a function of a number of factors, namely; the porosity of the fabric and its weight per square yard, the speed of fabric travel through the chamber, the heat of vaporization of volatiles and the softening temperature tolerance of the fabric. If one heat chamber does not meet the requirements for a specific fabric, multiple units in a line may be employed.

As the glass fabric comes out of the heating chamber or the post-scouring unit, it is completely devoid of interfiber protection and a protective coating must be applied at once. To accomplish this, the fabric from which the size has been removed may be fed in one or more baths of water soluble or dispersible resins, pigments, plasticizers, softeners and water repellants, the baths or padders operating in conjunction with suitable curing ovens. The finishing of the glass fabric subsequent to cleaning thereof forms no part of the present invention and the details thereof will not be further discussed.

The speed of operation within the heating chamber and the temperature of the heated air impinging on the fabric surfaces act to volatilize the organic substances on the fabric but give no opportunity for combustion within the chamber. Combustion, however, may be permitted at the exhaust of the suction blower 23. The heat of combustion may be used to pre-heat air being fed into the heater 22 to effect a further heating economy.

In one working embodiment of a chamber in accordance with the invention, intended for a maximum fabric width of 72 inches, the overall width of the chamber is 116 inches and the overall length of the chamber in the direction of fabric movement is 96 inches. The adjustable rate of ventilation is 200 to 600 cubic feet of air per minute, the temperature of air being controllable from 200 to 1400 degrees Fahrenheit. The temperature uniformity of impingement is maintained within plus or minus 10 F., the rate of heat transfer to fabric, with 200 F. drop of recirculated air, based on a 16 oz. fabric and 150 feet per minute: 1,300,000 B.t.u./hr. and 18,000 c.f.m.

While there has been shown What it considered to be a preferred embodiment of the invention, it is to be understood that many changes and modifications may be made therein without departing from the essential spirit of the invention as defined in the annexed claims. The invention, for example, is also applicable to the cleaning of other inorganic fibers, such as quartz and asbestos. The invention may also be carried out in some situations without a pre-scouring operation.

What I claim is:

1. A continuous method of cleaning an advancing fabric having woven yarns formed of inorganic fibers protectively coated with sizing materials comprising the steps of preheating air to a temperature above 200 F., impinging said preheated air upon the surfaces of the advancing fabric to heat the fabric to a temperature sufficient to volatilize the sizing material thereon, and withdrawing the heated exhaust gases including volatilization products from said fabric without combustion at the surface thereof.

2. The method of claim 1 in which said inorganic fibers are glass.

3. A continuous method of cleaning an advancing fabric having woven yarns formed of inorganic fibers protectively coated with sizing materials comprising the steps of pre-heating air to a temperature above 200 F., mixing recirculated exhaust gases with said preheated air, impinging the mixture upon the surfaces of the advancing fabric to heat the fabric to a temperature sufficient to volatilize the sizing materials thereon, withdrawing the heated exhaust gases including the volatilization products from said fabric without combustion at the surfaces thereof, and recirculating at least a portion of said exhaust gases.

4. A continuous method of cleaning an advancing fabric having woven yarns formed of inorganic fibers protectively coated with sizing materials comprising the steps of mixing recirculated exhaust gases with air, preheating the mixture of exhaust gases and air to a temperature above 200 F., impinging said mixture upon the surfaces of the advancing fabric to heat the fabric to a temperature suflicient to volatilize the sizing materials thereon, withdrawing the heated exhaust gases including the volatilization products from said fabric without combustion at the surfaces thereof, and recirculating at least a portion of said heated exhaust gases.

5. A continuous method of cleaning a moving fabric having fibrous glass yarns protectively coated with sizing materials comprising the steps of preheating air to a temperature above 200 F., conveying the fabric in open width condition through a chamber in which each transverse zone of the fabric is subjected to a series of alternate operations constituted by impingement of said preheated air upon the surfaces of the moving fabric to heat the fabric to a temperature sufficient to volatilize the sizing materials thereon, and withdrawing heated exhaust gases including volatilization products from the surface of the fabric, said conveyance being carried out at a speed which for the temperatures involved prevents combustion at the surfaces of the fabric.

6. A continuous method of cleaning a moving fiber glass fabric whose yarns are coated with sizing materials comprising the steps of scouring said fabric to removing a portion of said sizing materials, preheating air to a temperature of about 200 F., impinging said preheated air upon the surfaces of said moving fabric to heat the fabric to a temperature suflicient to volatilize residual sizing materials thereon, and withdrawing the heated exhaust gases including volatilization products from said fabric Without combustion at the surfaces thereof.

7. A continuous method of cleaning and weave setting an advancing woven fiber glass fabric Whose yarns are protectively coated with sizing materials comprising the steps of preheating air, impinging said preheated air upon the surfaces of the advancing fabric to heat the fabric to a weave setting temperature sufficient to volatilize the sizing materials thereon and to relax the fiber glass, and withdrawing the heated exhaust gases including volatilization products from said fabric without combustion at the surfaces thereof.

8. A continuous method of cleaning and weave setting an advancing woven fiber glass fabric whose yarns are protectively coated with sizing materials comprising the steps of preheating air, mixing said preheated air with recirculated exhaust gases, impinging the mixture upon the surfaces of the advancing fabric to heat the fabric to a Weave setting temperature sufiicient to volatilize the sizing materials thereon and to relax the fiber glass, withdrawing the heated exhaust gases including volatilization products from the fabric without combustion at the surfaces thereof, and recirculating at least a portion of said exhaust gases.

9. A continuous method of cleaning and weave setting an advancing woven fiber glass fabric whose yarns are protectively coated with sizing materials comprising the steps of mixing recirculated exhaust gases with air, preheating the mixture of exhaust gases and air, impinging said mixture upon the surfaces of the advancing fabric to heat the fabric to a weave setting temperature sufficient to volatilize the sizing materials thereon and to relax the fiber glass, withdrawing the heated exhaust gases including volatilization products from the fabric without combustion at the surfaces thereof, and recirculating at least a portion of said exhaust gases.

10- A process for treating a sized unfinished glass fabric comprising the steps of washing said fabric to reduce the size on the fabric to between 0.05 to 1.6% by weight, then raising the thus desized fabric to a weave setting temperature and maintaining the desized fabric at said temperature for a time sufficient to volatilize substantially all of the remaining size and to set the fibers, While diffusing the volatilized size with air to prevent combustion adj acent the fabric at said temperature.

References Cited by the Examiner UNITED STATES PATENTS 1,375,663 4/1921 Ainsworth 13415 2,674,549 4/1954 BalZ 134-2 2,862,305 12/1958 Dungler 34155 3,008,846 11/1961 Caroselli 1l7126 DONALL H. SYLVESTER, Primary Examiner.

DONALD W. PARKER, MORRIS O. WOLK,

Examiners.

H. G. GARNER, P. GILDSTEIN, C. E. VANHORN,

R. L. LINDSAY, Assistant Examiners. 

1. A CONTINUOUS METHOD OF CLEANING AN ADVANCING FABRIC HAVING WOVEN YARNS FORMED OF INORGANIC FIBERS PROTECTIVELY COATED WITH SIZING MATERIALS COMPRISING THE STEPS OF PREHEATING AIR TO A TEMPERATURE ABOVE 200*F., IMPINGING SAID PREHEATED AIR UPON THE SURFACE OF THE ADVANCING FABRIC TO HAT THE FABRIC TO A TEMPERATURE SUFFICIENT TO VOLATILIZE THE SIZING MATERIAL THEREON, AND WITHDRAWING THE HEATED EXHAUST GASES INCLUDING VOLATILIZATION PRODUCTS FROM SAID FABRIC WITHOUT COMBUSTION AT THE SURFACE THEREOF. 